Nedarim 11A

גמ׳ סברוה: מאי ״לחולין״⁠ — לא לחולין ליהוי, אלא קרבן.

Talmud: They assumed: What is the meaning of the term laḥullin? The individual is saying: It should not [la] be non-sacred [ḥullin] but rather it should have the status of an offering.

מני מתניתין? אי רבי מאיר ⁠— לית ליה מכלל לאו אתה שומע הן. דתנן, רבי מאיר אומר: כל תנאי שאינו כתנאי בני גד ובני ראובן ⁠— אינו תנאי.

The Talmud says: Whose opinion is expressed in the Mishnah? If you say it is that of R' Meir, he does not hold that from a negative statement you can infer a positive statement. As we learned in a Mishnah: R' Meir says that any condition that is not like the condition of the sons of the tribe of Gad and the sons of the tribe of Reuben, when Moses gave them land on the eastern bank of the Jordan River (see Numbers 32:29–30), is not a valid condition. Moses phrased the agreement as a double condition, stating that if they would join the other tribes in battle they would receive their inheritance on the eastern bank of the Jordan River, and if not, they would not receive that territory. Because R' Meir holds that only a condition expressed in this manner is valid, it is clear that he holds that one may not infer a negative statement from a positive one or vice versa.

אלא רבי יהודה היא. אימא סיפא, רבי יהודה אומר: האומר ״ירושלים״⁠ — לא אמר כלום. מדסיפא רבי יהודה ⁠— רישא לאו רבי יהודה היא!

Rather, the Mishnah is in accordance with the opinion of R' Yehuda. The Talmud challenges this statement: Say the latter clause of the Mishnah: R' Yehuda says: One who says that an item should be considered Jerusalem has not said anything. From the fact that the latter clause is stated by R' Yehuda, it is clear that the first clause is not in accordance with the opinion of R' Yehuda.